The present disclosure relates to a sheet feeder for feeding a sheet such as a document to a predetermined document reading position and an image forming apparatus with the same.
An image forming apparatus such as a copier includes a sheet feeder for conveying a document sheet such as a document with an image to a predetermined reading position, an image reader for reading a document image of a document sheet at the reading position to obtain image data, and an image forming unit for forming an image based on image data on a recording sheet.
The sheet feeder includes, as basic constituent elements, a pickup roller for feeding document sheets placed on a sheet tray one by one to a conveyance path, a feed roller for further feeding a document sheet picked up by the pickup roller to the conveyance path, a plurality of conveyor roller pairs for conveying a document sheet to a document reading position and a cover unit holding these members while allowing the rotation thereof.
Such a sheet feeder also includes a stopper. The stopper is a member arranged between the pickup roller and the feed roller and comes into contact with the leading end in a feeding direction of a document sheet placed on the sheet tray to restrict the position of the leading end in the feeding direction, i.e. align the position of the leading end in the feeding direction before a feeding operation by the pickup roller. By aligning the position of the leading end in the feeding direction, it is suppressed that the document sheet is fed in an oblique posture to the conveyance path at the time of the feeding operation by the pickup roller.
In a conventional sheet feeder using such a stopper, the stopper is coupled to a drive shaft of a pickup roller via a one-way clutch. When a document sheet is placed on a sheet tray and the leading end thereof in a feeding direction comes into contact with the stopper, a load of a drive system acts on the stopper via the one-way clutch, wherefore the stopper can specify the position of the leading end in the feeding direction. On the other hand, when the drive shaft of the pickup roller rotates, the load of the drive system acting on the stopper is released by the action of the one-way clutch and the stopper is pushed up (rotated) by a pressing force given by the document sheet being fed, thereby being separated from the leading end in the feeding direction. In this way, the document sheet is fed to the conveyance path.
In the above sheet feeder constructed as described above, when a jam occurs due to a feeding operation by the pickup roller or the feed roller, a user can remove the jammed document sheet by opening the cover unit and exposing the conveyance path to the outside. However, if the user does not know about the procedure of such a jam process, he tries to grab a part (e.g. trailing end in the feeding direction) of a jammed document sheet and forcibly pull out the jammed sheet from the conveyance path if the document sheet is jammed and the trailing end in feeding direction remains on the sheet tray. Thus, the stopper is likely to be caught by the document sheet being pulled out. If the stopper is caught by the document sheet, the document sheet may be torn.
Accordingly, in view of the above situation, an object of the present disclosure is to provide a sheet feeder capable of suppressing document sheet breakage even if a jammed document sheet is forcibly pulled out and an image forming apparatus with the same.